libavfilter: export ff_default_query_formats()

Its needed for fate on shared versioned .so
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/libavfilter.v

 LIBAVFILTER_$MAJOR {
         global: avfilter_*; av_*;
+            ff_default_query_formats;
         local: *;
 };